1. Field
This disclosure relates to a rechargeable lithium battery.
2. Description of the Related Art
Recently, due to reductions in the size and weight of portable electronic equipment, portable electronic equipment is increasingly being used. A battery having a high energy density for use as a power source of such portable electronic equipment is needed, and thus, research into a rechargeable lithium battery has been actively conducted. For a positive active material of a rechargeable lithium battery, a lithium-transition element oxide has been used. For a negative active material, a crystalline or amorphous carbon-based material or carbon composite has been used. To fabricate positive and negative electrodes, either the positive and negative active materials are coated on a current collector at an appropriate thickness, or the positive and negative active materials are made in the form of a film. To fabricate an electrode assembly, the positive and negative electrodes are then wound or stacked with an insulating separator interposed therebetween. The electrode assembly is put into a can or another case, and an electrolyte solution is injected to fabricate a prismatic rechargeable battery. Compared to using a can as a battery container, using a pouch as a battery container is advantageous in that the shape of the pouch may be flexibly changed and the size of the pouch may be increased. However, the pouch-type battery container is disadvantageous in that it may be easily deformed and damaged by external physical impact and it may be swollen when exposed to high temperatures. Such disadvantages become more serious in a rechargeable lithium battery using a liquid electrolyte solution than in a rechargeable lithium battery using a polymer electrolyte. Therefore, a pouch-type battery container is usually used with polymer electrolyte rechargeable lithium batteries. The polymer electrolyte rechargeable lithium battery has advantages such as not leaking, improved safety, improved high-temperature stability, and it may be more resistant to external physical impact. However, when the physical strength of the battery is increased in order to increase the resistance against external physical impact, the performance of the battery may be deteriorated due to an increase in internal resistance.